Microalgae represent a suitable and eco-sustainable resource for human needs thanks to their fast growth ability, together with the great diversity in species and intracellular secondary bioactive metabolites. These high-added-value compounds are of great interest for human health or animal feed. The intracellular content of these valuable compound families is tightly associated with the microalgal biological state and responds to environmental cues, e.g., light. Our study develops a Biotechnological response curve strategy exploring the bioactive metabolites synthesis in the marine cyanobacterium Spirulina subsalsa over a light energy gradient. The Relative Light energy index generated in our study integrates the red, green and blue photon flux density with their relative photon energy. The Biotechnological response curve combined biochemical analysis of the macromolecular composition (total protein, lipid, and carbohydrate content), total sterols, polyphenols and flavonoids, caroteno